Impedance tube – Precise measurement of sound absorption for technical sound insulation
An impedance tube is a measuring instrument used to determine the sound absorption and reflection properties of materials. It is used in acoustics and technical sound insulation to analyse how well a material absorbs or reflects sound waves. The impedance tube plays an important role in the development of high-performance sound insulation materials, particularly in automotive engineering, mechanical engineering and sound insulation for buses.
Cellofoam has its own impedance tube, which we use to carry out measurements and optimise the acoustic effectiveness of our sound insulation products. This ensures that our materials meet the highest requirements in vehicle, machine and building acoustics.
How does an impedance tube work?
An impedance tube (tube according to ISO 10534-2) consists of a cylindrical tube in which sound waves are generated by a loudspeaker.
Measurement procedure in the impedance tube:
- A microphone measures the reflection and absorption of sound on a material sample.
- The absorption coefficient (α) is determined in order to analyse the sound absorption properties.
- The results help to optimise materials for machines, vehicles and buses.
Cellofoam sound insulation solutions based on impedance tube measurements
Using the impedance tube, Cellofoam develops targeted, effective sound insulation and absorption solutions for technical applications:
✔ Sound absorbers & acoustic foams – Optimised materials for engine compartment insulation & passenger areas
✔ Heavy foils & composite materials – Combined insulation materials for reducing structure-borne noise & airborne noise
✔ Sound-insulating cladding for buses & vehicles – Precisely measured solutions for less driving noise & greater comfort
✔ Machine & plant insulation – Specially tested materials for reduced noise pollution in industrial plants
Applications of impedance tube-optimised insulation
- Vehicle technology & buses
Reduction of engine, transmission and chassis noise
- Mechanical engineering & industry
Precise sound insulation for production halls and technical facilities
- Rail vehicles
Noise protection in engines, passenger areas and cabins
- HVAC & heat pumps
Noise reduction in ventilation and air conditioning systems
Why are impedance tube measurements important?
✔ Precise sound absorption measurement – scientifically based optimisation of soundproofing materials
✔ Better acoustics for machines and vehicles – reduced noise emissions for greater comfort
✔ Effective technical soundproofing – targeted noise reduction for industrial and vehicle construction
✔ Compliance with noise protection regulations – materials with proven acoustic effectiveness
Conclusion
The impedance tube is a key instrument for developing highly effective sound insulation solutions. Using our in-house impedance tube, Cellofoam carries out precise measurements to optimise the sound absorption of our products in a targeted manner. This enables us to efficiently reduce noise in machines, vehicles and buses, ensuring more pleasant acoustics and higher product quality.